In vitro evaluation of air bubbles entrapped in composite restorations

Light-curing composite resin restorations are usually placed and cured in increments for large cavity due to their limited curing depth; the procedure may incorporate air bubbles into restoration. Objectives: The objective of this study is to evaluate the porosity of direct composite resin restorations placed and cured in increments. Methods: Three light-curing composite resins (Z100, Z250 and Charisma), packaged both in capsules and bulk syringes, were placed and cured in a cavity mold in three increments of 2 mm thick each, respectively, with a curing time of 20-second for each layer. Three restorations were prepared for each material and each packaging, and the restorations were then cut longitudinally into slices of 0.3 mm in thickness. Five slices of each restoration were observed under microscope and the number of air bubbles was counted. Three control samples were prepared for each material and each packaging by light curing the extruded resin from capsule or syringe directly without any inserting. Data were analyzed by ANOVA.Results: All the restorations filled in increments presented significantly more bubbles than that of the control (P<0.01), and the restoration filled with syringe packing materials showed more bubbles than that with capsule packing materials (P<0.01).